Multiple Resonant Peaks Research Articles

Multiple resonance peaks of FeCo thin films with NiFe underlayer

Under zero external magnetic fields, single-layer FeCo thin films exhibit no ferromagnetic resonance (FMR) peaks, while multiple FMR peaks were obtained by growing FeCo thin films on NiFe underlayers with various thicknesses up to 50 nm. Comprehensive investigations of the dynamic magnetic properties and origin of the peaks were conducted through measurements of microwave permeability via a shorted microstrip perturbation technique. Through fitted values of saturation magnetization Ms, uniaxial anisotropy HKsta, and rotatable anisotropy HKrot extracted from the FMR experiments, it was found that two of the three resonance peaks originate from FeCo, and the third from NiFe. The two magnetic phases of FeCo grains are found to have different values of HKrot and explained by the exchange interaction between FeCo and NiFe grains.

Enriched vibrational resonance in certain discrete systems

We wish to report the occurrence of vibrational resonance in certain discrete systems like sine square map and sine circle map, in a unique fashion, comprising of multiple resonant peaks which pave the way for enrichment. As the systems of our choice are capable of exhibiting vibrational resonance behaviour unlike the earlier reports, they are taken for investigation and the necessary numerical and analytical results are presented. Further, we study the effect of external forcing on various attractors of these systems with appropriate bifurcation and Lyapunov exponent diagrams.

Height-related magnetoelectric performance of PZT/Ni layered composites

The effect of height on performance of the PZT/Ni cylindrical bilayered magnetoelectric (ME) composites was studied in situ in this paper. Multiple resonant peaks appear between 1 and 300 kHz frequency for cylinders of different heights. The first resonance frequency does not change with the cylinder height decreasing, but the second and the third resonant frequencies increase. The first three resonant modes are attributed to the cylinder radial, first-order height resonance, and second-order height resonance, respectively. The appropriate size and resonance frequency were chosen to obtain the highest ME voltage coefficient when designing cylindrical bilayered magnetoelectric devices. This article provides reference to design cylindrical magnetoelectric devices.

Synthesis of hierarchical sword-like cobalt particles and their microwave absorption properties

In this paper, we reported synthesis of the cobalt particles with a hierarchical sword-like structure through a liquid reduction method. We have investigated the electromagnetic properties of the cobalt particles in the microwave frequency range of 2–18 GHz. The cobalt particles presented multiple dielectric and magnetic resonance peaks, which are related to their unique structure. We have predicted the microwave absorption properties of the cobalt particles according to the transmit line theory. The maximum reflection loss (RL) of the cobalt particles reaches −60.13 dB, and the effective absorption bandwidth (RL ≤ −10 dB) is 5.42 GHz corresponding to a thickness of 1.4 mm, revealing better microwave absorption than previously reported materials. The superior microwave absorption properties indicate that the as-prepared cobalt particles have potential application as candidates for microwave absorption.

Enhancing detection sensitivity of metallic nanostructures by resonant coupling mode and spectral integration analysis.

We report a simple method to efficiently improve the detection limit of surface plasmon resonance in periodic metallic nanostructures by using small angle illumination and spectral integration analysis. The large-area gold nanoslit arrays were fabricated by thermal-annealing template-stripping method with a slit width of 60 nm and period of 500 nm. The small angle illumination induced a resonant coupling between surface plasmon mode and substrate mode. It increased ~2.24 times intensity sensitivity at 5.5° incident angle. The small-angle illumination also resulted in multiple resonant peaks. The spectral integration method integrated all changes near the resonant peaks and increased the signal to noise ratio about 5 times as compared to single-wavelength intensity analysis. Combining both small angle and spectral integration, the detection limit was increased to one order of magnitude. The improvement of the detection limit for antigen-antibody interactions was demonstrated.

Effects of wind-driven telescope vibrations on measurements of turbulent angle-of-arrival fluctuations.

Turbulence in the atmospheric refractive-index field causes optical angle-of-arrival (AOA) fluctuations that can be used for atmospheric remote sensing of various parameters, including wind velocities and the optical refractive-index turbulence structure parameter, C(n)2. If AOA measurements are contaminated by wind-induced telescope vibrations, the underlying retrieval algorithms may fail. In order to study the effects of wind-driven telescope vibrations on optical-turbulence measurements, we conducted a field experiment in which we exposed two small telescopes deliberately to the wind. We measured AOA fluctuations of visible light propagating along a horizontal, 174 m long path 1.7 m above flat terrain, and we used fast-response ultrasonic anemometers to measure the wind velocity at multiple locations along the path. We found (1) that the AOA turbulence spectra were contaminated by multiple resonance peaks, (2) that the resonance frequencies were independent of the wind speed, and (3) that the AOA variance associated with the dominating vibration mode was proportional to the fourth power of the wind speed.

A universal scaling law of grain chain elasticity under pressure revealed by a simple force vibration method.

The grain contact force, the key player in determining the mechanical properties of grain materials, depends on the elastic modulus and deformation (δ) of grains. However, our knowledge on their relationship in a three-dimensional granular medium is limited mainly owing to the difficulty of realizing direct experimental investigation. Using a simple force vibration technique, we measure the dissipation spectra (the frequency response) of three kinds of grains with different elastic moduli under different pressures (to change the grain deformation). The dissipation spectra exhibit multiple resonant peaks, indicative of the resonance of grain chains with different lengths. This allows us to quantitatively characterize the elastic behaviors of grain chains. A universal correlation of the resonant frequency (f) of a grain chain with deformation is observed for all granular systems with different material properties (Young's modulus E, density ρ and Poisson's coefficient ν): f(2) ∝ δ(1/2)E/ρ(1 - ν). The deformation of the grain chain under pressure follows a p(2/3) pressure dependence. This general behavior suggests that the pressure-induced deformation of the grain chain under low-frequency weak shear vibration is overwhelmed by the nonlinear Hertzian contact elasticity.

Resolving multiple peaks using a sub-transit-linewidth cross-correlation resonance

In a recent paper [L. Feng et al., Phys. Rev. Lett. 109, 233006 (2012)], we demonstrated a sub-transit-linewidth resonance based on cross correlation between optical fields in an electromagnetically induced transparency (EIT) system. Here, we investigate the ability of such resonance to resolve multiple resonance peaks. We first report the implementation of the cross-correlation resonance in a hyperfine EIT system, with a linewidth of about $1/16$ of the transit EIT width. Then, a magnetic field is applied to create multipeak EIT resonance with tunable spacing. Cross-correlation resonance with multipeaks is observed and the line shape agrees qualitatively with our numerical simulations. We find that the multipeak correlation resonance has better contrast than the corresponding EIT resonance, but with a lower signal to noise. Furthermore, this correlation resonance cannot resolve peaks with spacing close to or less than the intrinsic width, like any other resonance techniques. We analyze the origin of this limitation and make connections to the Ramsey-type subnatural spectroscopy technique. This work shows potential applications of the correlation resonance in atomic frequency standard and laser spectroscopy.

Thermally driven classical Heisenberg model in 1D with a local time varying field

We study thermal transport in the one-dimensional classical Heisenberg model driven by boundary heat baths and in the presence of a local time varying magnetic field. We find that, in the steady state, the energy current shows thermal resonance as the frequency of the time-periodic forcing is varied. Even in the absence of a thermal bias a steady nonzero energy current can be induced in the system, whereas for the thermally driven system a current reversal can be achieved in the bulk by suitably tuning the system parameters. When the amplitude of the forcing field is increased the system exhibits multiple resonance peaks. Thermal resonance survives in the thermodynamic limit and their magnitude increases as the temperature of the system is decreased. We find that the resonance frequency is an intrinsic frequency of the model and is related to its spin wave dispersion spectrum. Finally we show that, similar to other generic force-driven systems, there is no thermal pumping despite the current reversal in the bulk of the system.

Distributed discrimination of strain and temperature based on Brillouin dynamic grating in an optical fiber

This paper reviews distributed discrimination of strain and temperature by use of an optical fiber based on fiber optic nerve systems. The preliminary method based on multiple resonance peaks of the Brillouin gain spectrum in a specially-designed fiber is firstly introduced. The complete discrimination of strain and temperature based on the Brillouin dynamic grating in a polarization maintaining fiber is extensively presented. The basic principle and two experimental schemes of distributed discrimination based on fiber optic nerve systems are demonstrated. The performance of the high discriminative accuracy (0.1 °C–0.3°C and 5 μɛ–12μɛ) and high spatial resolution (∼10 cm) with the effective measurement points of about 50 for a standard system configuration or about 1000 for a modified one will be highly expected in real industry applications.

Thermal stability of high frequency properties of gradient-composition-sputtered FeCoHf films with and without stripe domains

A systematic study on the thickness dependence of dynamic magnetic properties and their thermal stability behaviors of FeCoHf thin films grown by gradient-composition sputtering technique was carried out. The critical thickness for the formation of stripe domain structures at room temperature was found to be around 120 nm based on the appearance of the multiple resonance peaks and the shape of the magnetization curves. For the films with thicknesses less than 90 nm, the ferromagnetic resonance frequency and in-plane magnetic anisotropy are increased with the increasing of temperature; however, for the films with thicknesses in the range from 90 nm to 120 nm, the ferromagnetic resonance frequency is reduced with temperature and the secondary peak appears as the temperature is raised suggesting an evolution of stripe domains. For the films with stripe domains at room temperature, the ferromagnetic resonance frequency is also decreased with increasing temperature, and in some cases, there is a splitting up of the resonance peaks indicating that there is a change in the stripe domain states when the sample is heated up. All the results are discussed considering the contribution of stress-induced magnetic anisotropy and the increasing of a weak perpendicular magnetic anisotropy.

Multiple nonlinear dielectric resonance of ultra-long silver trimolybdate nanowires

Abstract The silver molybdate nanowires (NWs) have been synthesized and characterized. The multiple dielectric resonant peaks of the nanocomposites filled with silver molybdate nanowires have been studied from 2 to 18 GHz. The as-established equivalent circuit model of the silver molybdate nanowires were employed to explain the nonlinear dielectric resonant behavior.

VIBRATION SUPPRESSION OF TRAIN-INDUCED MULTIPLE RESONANT RESPONSES OF TWO-SPAN CONTINUOUS BRIDGES USING VE DAMPERS

This paper presents a study of reducing multiple resonant peaks of high-speed trains traveling over a two-span continuous railway bridge using visco-elastic (VE) dampers. The moving train is modeled as a series of two-degree-of-freedom (2 DOF) moving oscillators with identical intervals and the two-span continuous bridge as a Bernoulli-Euler beam with uniform span. Because of closely spaced frequencies of a continuous beam, the first several frequencies of the bridge would be excited to resonance during the passage of moving trains, which may result in multiple resonant peaks appearing on the response of train-bridge system. In order to reduce the multiple resonant peaks of both the high-speed trains and the two-span continuous bridge, VE dampers are installed at the bottom of the bridge deck to absorb the vibrating energy transmitted from the bridge. From the numerical investigations, the inclusion of VE dampers is useful to simultaneously suppress the multiple resonant peaks of train-bridge system and further improves the riding comfort of moving vehicles. Meanwhile, the strategy of arranging the VE dampers on the continuous bridge is also investigated.

Tunable Multichannel Filter in a Photonic Crystal Containing Semiconductor Photonic Quantum Well

A tunable multichannel filter in the finite photonic crystal (PC) containing photonic quantum well (PQW) as a defect is proposed. The symmetric structure (AB) <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> (CD) <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> ( BA) <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> and the asymmetric structure (AB) <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> (CD) <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> (AB) <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> are considered in this work. Here, the host PC of (AB) <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> is made of Si for layer A and of SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> for layer B. In the PQW, (CD) <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> , C also is Si, but D is an extrinsic semiconductor, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -type silicon ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -Si). With the use of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -Si, it is found that both structures can function as a tunable multichannel filter in the infrared region. The number of channels is equal to <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> + 1 in the symmetric structure, whereas it is <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> for the asymmetric one. The positions of multiple resonant peaks can be tuned by the variation in the impurity concentration of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -Si. The proposed filter could be used to design the wavelength division multiplexer filter that is of technical use in optical communications.

Resonant X-Ray Diffraction Study of an Unusually Large Phase Coexistence in Smectic Liquid-Crystal Films

The recent discovery of the new smectic-C(d6)(*) (SmC(d6)(*)) phase [S. Wang et al., Phys. Rev. Lett. 104, 027801 (2010)] also revealed the existence of a noisy region in the temperature window between the SmC(d6)(*) phase and the smectic-C(d4)(*) (SmC(d4)(*)) phase. Characterized by multiple resonant peaks spanning a wide region in Q(Z), the corresponding structure of this temperature window has been a mystery. In this Letter, through a careful resonant x-ray diffraction study and simulations of the diffraction spectra, we show that this region is in fact an unusually large coexistence region of the SmC(d6)(*) phase and the SmC(d4)(*) phase. The structure of the noisy region is found to be a heterogeneous mixture of local SmC(d6)(*) and SmC(d4)(*) orders on the sub-μm scale.

Multiresonance of energy transport and absence of heat pump in a force-driven lattice

Energy transport control in low dimensional nanoscale systems has attracted much attention in recent years. In this paper, we investigate the energy transport properties of the Frenkel-Kontorova lattice subject to a periodic driving force, in particular, the resonance behavior of the energy current by varying the external driving frequency. It is discovered that, in certain parameter ranges, multiple resonance peaks, instead of a single resonance, emerge. By comparing the nonlinear lattice model with a harmonic chain, we unravel the underlying physical mechanism for such a resonance phenomenon. Other parameter dependencies of the resonance behavior are examined as well. Finally, we demonstrate that heat pumping is actually absent in this force-driven model.

A mid-infrared tunable filter in a semiconductor–dielectric photonic crystal containing doped semiconductor defect

In this work, we theoretically analyze tunable filtering properties in a semiconductor–dielectric photonic crystal (SDPC) containing doped semiconductor defect in the mid-infrared frequency region. We consider two possible configurations of filter structures, the symmetric and asymmetric ones. With a defect of the doped n-type semiconductor, n-Si, the resonant transmission peak can be tuned by varying the doping concentration, that is, the peak wavelength will be shifted to the position of lower wavelength for both structures. Additionally, by increasing the defect thickness, it is also possible to have a filter with multiple resonant peaks, leading to a multichannel filter. The results provide another type of tunable filter in the defective SDPC that could be of technical use for semiconductor applications in optical electronics.

Origin of localized surface plasmon resonances in thin silver film over nanosphere patterns

Film over nanosphere (FON) patterns are formed by depositing a silver film on top of a close-packed polystyrene (PS) sphere template. Multiple localized surface plasmon resonance (LSPR) peaks are experimentally measured in the three-dimensional FON pattern for thin silver films. Increasing the sphere size in the close-packed template or the deposited silver film thickness red shifts the LSPR peaks to varying degrees. A finite difference time domain analysis reveals that the main LSPR peaks originate from a quadrupole and a dipole coupling mode near the triangle gap surrounded by three adjacent PS spheres. The physical location and the electromagnetic enhancement of the two resonant modes are determined for different thicknesses of deposited silver films.

Tilted Fiber Bragg Grating for Chirped Microwave Waveform Generation

A tilted fiber Bragg grating (TFBG) as an optical spectral shaper to generate a chirped microwave waveform in a spectral-shaping and wavelength-to-time (SS-WTT) mapping system is proposed and demonstrated. The key component in the system is the TFBG, which has multiple resonant peaks with linearly increasing spacing in its transmission spectrum. By incorporating a TFBG into an SS-WTT system, a chirped microwave waveform is generated with the chirp rate determined by the tilt angle of the TFBG. A proof-of-concept experiment is carried out. Two TFBGs with tilt angles of 10 and 4 are fabricated and employed to generate two chirped microwave waveforms with chirp rates of 0.00700 and 0.05956 GHz/ps, respectively.

Mixed-frame and stationary-frame repetitive control schemes for compensating typical load and grid harmonics

In this study, repetitive current controllers operating in either the mixed or stationary frame are proposed for high-precision reference tracking and disturbance rejection of power converters. Both controllers use a proportional-resonant regulator in the stationary frame for regulating the positive- and negative-sequence fundamental currents, which are known to directly influence the flow of active and reactive power in most energy conversion systems. Moreover, for the tracking or compensation of harmonics, the controllers include a repetitive control path in either the synchronous or stationary frame, whose inherent feedback and feedforward structure is proven to resemble a bank of resonant filters in either reference frames. Unlike other existing controllers, the proposed repetitive controllers function by introducing multiple resonant peaks at only those harmonic frequencies typically produced by most non-linear loads, with no high-resonant gain introduced at all other non-characteristic components. Hence, they are expected to be more robust and less sensitive to implementation noises. By performing synchronous transformation using an unfiltered angle or by using its equivalent frequency-shifted variant, the tracking abilities of the controllers are also shown to remain undisturbed even if a distorted grid or back-emf source is intentionally connected to the system. These described performance features, together with the controller simple implementations, were physically tested with a digitally controlled commercial converter.